Gastric mucosal cells from the mouse stomach will be dissociated by pronase digestion and various parameters of viability will be determined. These will include dye exclusion, oxygen depletion, substrate incorporation, and ultrastructural integrity. Velocity sedimentation technique for separating cells according to size has been adapted to produce highly enriched parietal cell fractions with a purity of 75 to 95%; and small cell fractions with less than 2% parietal cells are also separated. In addition a fraction of chief cells is also distinct. These mixed and purified cell populations will be used for further studies on the various physiological and biochemical aspects of these cells. Studies on pepsinogen distribution in various cell fractions as well as carbonic anhydrase activity will be explored. Uptake of labeled precursors indicating biosynthetic activity will be determined to assess their viability and specific synthetic activity. Electron microprobe analysis will be made on intact freeze-dried gastrin mucosa and in individual isolated cells for such elements as Cl, K, Na, S, Ca, and Mg.